Heat exchanger/flapper box hoses toast
 

In trying to troubleshoot the 76 heating system I decided to check out the flapper boxes and I discovered that the hoses going from the heat exchangers to the flapper boxes are completely destroyed! Its strange because both sides are almost Identical. I plan to replace the hoses and possibly the flapper boxes but my question is what kind of symptoms would this cause?
http://forums.pelicanparts.com/uploa...1517979301.jpg
http://forums.pelicanparts.com/uploa...1517979301.jpg

Yikes! The symptom would be no heat in the cabin. Replace the hoses & clamps. Oil the moving parts in the flappers. Confirm the engine compartment hoses are in better condition and the blower motor is working. Confirm the cable is fully opening and closing the flapper.

As someone said years ago here, for a few moments it will appear nothing is happening, then it suddenly becomes unbearably hot in the cabin.